Rangefinder-sights



Jan. 15, 1963' Filed Oct. 15, 1958 H. s. ToczYLowsKl 3,073,211

RANGEFINDER-SIGHTS '7 Sheets-Sheet 1 FIG. I.

- PRIOR ART FIG. 3

PRIOR ART INVENTOR:

H.8.. TOGZYLOWSKI Jan. 15, 1963 H. s. TOCZYLOWSKI 3,073,211

RANGEFINDER-SIGHTS Filed Oct. 13, 1958 7 Sheets-Sheet 2 FIG- 2A.

PRIOR ART FIG/2B- INVENTOR: H5. TOCZYLOVISKI yflwwwr a 2 fl orne ls Jan. 15, 1963 H. s. TOCZYLOWSKI 3,073,211

RANGEFINDER-SIGHTS med Oct. 15, 1958 7 Sheets-Sheet :5

FIG. 4

PRIOR ART FIG. 5.

IN VENTO R ".3. TO OZYLOWSKI %mm w@ Jan. 15 1963 H. s. TOCZYLOWSKI 3,073,211 i RANGEFINDER-SIGI-ITS ".5. rocznoviam Jan. 15, 1963 H. s. TOCZYLOWSKI 3,0

RANGEFINDER-SIGHTS Filed Oct. 13, 1958 I 7 Sheets-Sheet 5 F I 6.9 PRIOR ART FIG. IO.

mvsu'rom H. s. TOGZYLOWSKI imr/n llx Jan. 15, 1963 H. s. TOCZYLOWSKI 3, 7

RANGEFINDER-SIGHTS Filed Oct. 13, 1958 7 Sheets-Sheet 6 FIG- ll PRIOR ART FIG- I2 PRIOR ART INVENTOR V1.5. TOCZYl-O Mafia/w ls Jan. 15, 1963 H. s. TOCZYLOWSKI 3,073,211

RANGEFINDER-SIGHTS Filed Oct. 15, 1958 7 Sheets-Sheet 7 Fl G. l6-

" is to. establish fwith thea'xis of' the barrel of th e weapon to. Y iahgefindensight iscla'mped' rangefinding system; in such? a'manne as to obtain weaponandl'ammuniti'o to jscore-ahitfa't United States atent 3,073,211 Patented Jan. 15, 1963 hoe This invention relates to optical rangefinder-sights,

whereby are meant instruments clamped to the barrel of a firing weapon which perform simultaneously the dual function of determining the range to a target and of providing fora suitable tangent elevation angle be tween the line-of-aim and the axis of the barrel as required for scoring a hit at the target.

The present application is a continuation-in-part of my co-pending application Serial No. 475,522, filed December 15, 1954, now abandoned.

A specific tangent elevation angle is required for any given range to compensate for the fall of the projectile when in flight between the muzzle of the Weapon and the target. Consequently the rangefinder-sights known to prior art provide for a specific and unique angular relationship between the barrel and the line-of-airn for any range determined by the setting of the ranging systom of the rangefinder-sight; said relationship being de termined by the ballistic properties of the Weapon and ammunition for which the rangefinder-sight is designed.

Consequently the rangefinder-sight cannot function properly when the ballistics of the weapon and ammunition change, unless some facility is incorporated in the rangefinder-sight which would make it possible,

at the range determined by the setting of the ranging system of the instrument.

Now the object of my invention is to improve the rangefincler-sights known to prior art by providing a novel and more. convenient means of catering for a plurality of ballistics of the weapon'to which the range: finder-sight is clamped. This is achieved by elfecting the ranging system of the rangefinder-sight whileth sighting system and the mechanical link between the ranging and sighting systems are left undisturbed,

Furthermore, as will be explained hereafter, theirrr,

provement according to my invention providesfor a for a given range, to alter the angular relationship between the line-of-aim and the banrel ,so as to obtain a tangent elevation angle to fit the changed ballistics; The new ballistics must be known beforehand. Facilities of this nature are incorporated in some rangefinden sights known to prior art, more specifically for the purpose of catering for changes in the ballistics of the weapon resulting from the use of ditferent kinds of ammunition.

It canfbe broadly stated that a rangefinder-sight of which many varieties are known consistsfessentially oi three elements; one is the rangefinding system, the second isthe sighting system and the third is a mechanism linking the rangefinding system withpthesighting jsys tern. The latter element is omitted insoir'ie'types of.

rangefinder-sights.

The purpose of the rangefinding system, of which many varieties are known, is to presentto the operator h an image or images of the tar-get in such a mannerthat F the aspectofsaidfimageor. images,tor' a given setting of said system-depends .itpon the range- Theranging is then accomplished. by operating :the rcont ols er lthe system until the image (or, images) of the ftarget is, Q brought to a prescribed aspect whereupon therange can be determined riom the position of thecontr'ol at which :aspect of the image of the-target 'is ob- The-117E 3 I either ofthe telescopic-or else of, theopen-s1ght variety,

line-of-aim' running through;

rt arget and, remaining in tangent. elevation angle ;r'equirfed by ballistic: f

f; the sighting" system, which can is the at atarget;

given range--'a selection of an infinite number of tan:

also iii some rangefinder-sights of the stereoscopic variety,

the ranging and sighting systems are fused into one.

A characteristic feature of the improvement according to my invention is that it may be applied to any type of rangefinder-sight known to prior art. To illustrate this point, in the following detailed description, my invention will be exemplified as applied to three specific rangefinder-sights of which one is of the image-t coincidence type, one of the image-distortion type and one of the stereoscopic type; this on the understanding that this method otpresentation should in no way be construed as restricting the application of the invention to the three instruments to be described detail.

; Withreference to the accompanying drawings;

FIG. 1 is a perspective view of a' rangefinder-sight mountedon. the barrel of a firing weapon and" trained FIG. 2A is a perspective View of the optical system and of the ranging and sighting mechanisms of, one ofthe stereoscopic rangefinder-sigh'ts known. to prior art, to

which my invention canbe applied.

FIG. 2B is a plan view of the optical system and of the elevating mechanism of the instrument of FIG 2A oni which the possible locationsof to be addedaccordingfto,my'inventionare indicatedj 3 is a diagrammatic 'viewlofjthe reticles in an" alternative, stereoscopic rangefinder-sight t0' which invention Can'be applied, t

' FIGQA is a perspeotive viewpf of the rangingand sighting mecha'nisms of one oflthe 'rangefinder-sights of the image-coincidence,varietyknew {to prior artto whichmy inventio can be appliedi rm. 5 'is .a plan View fo the optical" system of themstrument ,ofi-FIG; 4 show ggthe possible locations'of thev f additional element t be added according to-myinvenr,

- FIG.

the additional element.

the-optical systemandand when the initial ballistics prevail.

i directe towards 3 FIG. 9 is a diagram showing the field of vision of an image-distortion rangefinder-sight known to prior art and portrayed in FIGS. 6 and 7 when this instrumentis trained at a target.

FIG. 10 is a diagram showing the changes in the field of vision portrayed in FIG. 9 when the instrument is supplemented to incorporate the improvement according to the present invention.

FIG. 11 shows the control of an infinity adjustment in a rangefinder-sight known to prior art in its neutral position when there is no instrumental error.

j :FIG; 12 shows the control of FIG. llset to correct as'rnal'l instrumental error.

*FIG. 13 shows the control of an infinity adjustrnen modified according to one embodiment of my invention inits neutral position where there'is no instrumental error FIG. 14 shows the control of FIG. 13 set to correct -a small instrumental error when the initial ballistics stil'l prevail.

FIG. 15 shows the control of FIG. 13 set to correct a small instrumental error as per FIG. 14 and also to cater for modified ballistics.

FIG. 16 is a plot ,in Cartesian coordinates of three ballistic curves showing tangent elevation angles versus range.

FIG. 17 is a diagrammatic'view in perspective of a deviator embodied in my invention.

FIG. 18 is a view showing another embodiment of said I deviator.

With reference to FIG. 1, J is the rangefinder-sight in the form of an oblong box mounted athwart the barrel W of a firing weapon trained at a target T located at a range R. The rays of light emanating from. the target enter the instrument through a pair of windows I and 1' whose spacing B is the base of the instrument. In FIG. 1 and inother drawings to be discussed subsequently, the

rangefinder-sight is mounted on the weapon in such a manner that the base of :the instrument is horizontal;

however, the invention is equally applicable to range-. 1

finder-sightswith a vertical base.

I The parallax angle p which is the angle subtended by .the-baseTBof the instrument-when viewed from the target Tdependsupon the range R so that therange can be In the above equation, which is valid for small angles,

angle p is determinedi v With referenqeito Hos ZA-jand 2B,- the as or light I..- anc l; remanating from the target enter'the left The latter is the result of a subconscious process in the mind of the observer whereby the two images of the target, each viewed by one eye, are fused into one and a sense of distance is obtained according to the angular spacing between the two images corresponding to the parallax angle p of FEGJ.

Now if two identical markers 241 and 241 are ar-v ranged, one on each reticle ll and 161' respectively, then the operator will have the illusion of one marker being present in his three-dimensional field of vision. This marker may appear nearer or farther away than the target T, according to the spacing of the markers 241 and 241" on the two reticles.

It follows that if the spacing between the reticles with markers is varied, the operator will have the illusion of the single marker seen in three-dimensional space approaching or receding, according to whether the spacing of the actual markers is decreased or increased, and the apparent range of the virtual marker seen by the oper ator is a function of the spacing of the two reticles.

ing, whichis conventional, are not shown in FIG. 2A.. The upper end of the shaft 41} is threaded and so is a determined y m s ring p if B is known. (Il e ab 1 quantities arejlinked by the relation: 7 I V '50 n p, q is .a constant coefiicient depending on the units used." For-instance, if the length of the base B is expressed in inches andythe parallax angle p isexpressed in angular .miIsQthenein rder,to get the range R. in metreswe;

' alue ofyq must. bei, q=25.4; millimetres per inch): The i boveflequation'is the fundamental equation of allrangeders; they;difiergjin the mannerf in which'the par-allax .60 I -:andfright pentaprisms 111; and: :11! respectively where :;;j each'beanmsufiefistwoconsecutivereflections. The spac V i ng .lief/the"pentaptiisrr sfis fthe baseof the .rangefinder.

5 {When emergingi fr'om the pentaprisms; the beams are each other; .lithey; are icollimated in ob- 14 and 14rian'dent' Tia .pair'bffro'of prisms; -each beamfloyerf"' f thetargetj i of the markers 24! and Zr to vation angle of the firing In the instrument portrayed in FIG. 2 the two reticlesare fitted each with a roller 36r, 361 and are slidably mounted in a frame 37 so that their horizontal spacing can vary. The reticles are connected by a spiral spring 38 which urges them to converge by sliding along the frame while a cam 26, wedged between the reticle rollers, counteracts the action of the spring by pushing them apart. The reticle-carrying frame 37 is held between a pair of fixed vertical arms 381 and 3hr forming a pair of runners between which the frarne 37 can slide vertically. Y

A vertical shaft 4%, fitted with a control knob 23 at the lower. end, is rotatably fixed in the horizontal base so that it cannot move vertically. The details of-its fixniating hole in a bulge 39 of the framedr'. Therefore, when the knob 23 is rotated,- the shaft 40' andfrarne37 act on the screw-and-nut principle and the frame moves vertically up or down, depending on whether the knob 23 is rotated clockwise-or anticlockwise. Thexve'rtical displacement of the frame. 37 causes the horizontal spacing 7 change, because of the action ofthe cam and rollers.

' It follows that the'horizontal spacing, of the reticle markers MI and 24;, :whichdetermines the apparent range of the virtual single marker in-the-threedimernsion-al field of visionof theoperator, clependsj on the level.

of ther'na'rke'rsiin amuse; determinedby the shape'j of the earn, Inturn the lin'e-of-sight running to'the target; via the reticle markers determines a specific tangent ole-Q weapon to iwhichthe instrument:

is rigidly :clamped; J-

, It alsofollowsthat by suitablyfg'shapi'ng thejcamgze;

it is possible to establish -a relationship ibetweehtheiapparent/range of the. single marker zin theFfield ofvision ofthe operator andth'e. corresponding tangent elevation. offith'e v barrel which will. lit the ballistics of. the weapo three-consecutivesteps first to1operate the control knob I V I h hedjustableapparent range ofuthej-singlei h .thatipf -;the: target, isecp'nd ito lay to place: thejimageiof' the. rnarker age fof thej target, ,ftliird to pullthe Most atereotscopicrangefindersights iop'e'r ate v abo'v principle although .ztho

, diii er in the arrangementg;

- 6 of details of the mechanism which causes the apparent With referenceto FIG. 8 which shows a rangefinderdistance to the virtual single marker to vary. sight trained at a target T located. at a range R, the In some rangefinder-sights known to prior art the procimage of the target formed by the beam associated with ess is reversed: the horizontal spacing of the two markers the window r appears .to the right of that formed by the on the reticles does not change, so that the apparent beam associated withthe window lit the distance to the range of the single virtual marker present in the of point Tl ofintersection of the optical axes of the systems vision of the operator remains fixed. On the other hand associated with the windows I and r is shorter than the means are provided for deviating slightly one of the range R of the target. The position of the two images is beams of light in the horizontal plane, whereby all the reversed if the point of intersection T2 of the two optical actual objects viewed by the operator seem to approach 10 axes is located behind the target T. Finally the two or recede and ranging is done by matching the variable images of the target coincide if the two optical axes inapparent range of the target with the fixed apparent range tersect at the target. of the single marker. In order to be able to vary the parallax angle p, an As will be explained hereafter, the improvement acadjustable optical deviator must be placed in the path of cording to my invention is equally applicable to both one of the beams l or r so as to deflect the beam horifamilies of stereoscopic raugefinder-sights discussed above .ztmtall in a known and measurable manner. I and known to prior art. in the instrument shown in FIGS. 4 and 5 this devi- There is yet another stereoscopic rangeiindensight ator is in the form of a pair of identical optical wedges known to prior art to which the improvement accord- 18 and 19 placed in the path of the beam 1'. These ing to the present invention can be applied. The optical 20 wedges are mounted in circular frames fitted each with system of this instrument is identical to that portrayed a conical gear 2% and 21. These gears are meshedwith in FIGS. 2A and 23 except that the two movablercticles another conical gear 22 driven by a hand-operated knob carrying each one marker are replaced by two fixed 2 3 which is mounted'on a shaft protruding from the casreticles each carrying a pattern in the form of a train ing of the instrument so that it is accessibleto the opof markers as shown in FIG. 3. Consequently the mech- 25 erator. anisrn is omitted altogether so that the instrument fea- It is seen that when the knob 23 is rotated the wedges 18 tures no moving parts. and 1h rotate by the same amount in opposite directions. With reference to FIG. 3 the markers are arranged In the neutral position of the deviator the wedges 18 in pairs. Each pair of markersappears'at a diiierent and 39 are mounted so that the taper of one'points level and has a different spacing, so that as a result, a upwards and that of the-other downwards. Thus one detrain of virtual markers, each located at a diiiiercnt height fleets the beam upwards and the other downwards by and at a dilierent apparent range, is present in the field the same angle and the beam remains undeflected after of vision of the operator. The apparent ranges and passing through both wedges. heights of these virtual markers are so related to the Now if a wedge is rotated its deflection angle canrbe ballistics of the weapon that the three-dimensional locus resolved in two components: one vertical, theother horiof the train of markers presented to the operator follows Zon Th former decreases and the 0316i" increases as the line-of-flight of the projectile. Consequently the the rotation angle of the wedge increases. By rotating function of the operator is to train the Weapon in azimuth simultaneously the two identical wedges over equal angles, and elevation such a manner-as'to thread through one clockwise and-the other anticlockwise, as described the image of the target, the iine-of-fiight of the projectile 40 above, the vertical components of the deviation angles determined by the train of markers present in the field ofv remain equal and directed opposite each other while .the VlSlOl'l. horizontalcornponents also remain equal but are pointin FIGS. 4 and 5, which refer. toa rangefinder-sight ing in the same direction so that they add up and the; of the W pp g variety known to prior art, liand' total effect is a horizontal deviation of the beam rby and 11! and Mr are two pentaprisms .whose spacing B r are again two beams of light emanating from the target fin amount depending P rotation angle i the knob 23 and in a direction depending upon the direction is the base of the instrument, of rotation of said knob. I .Y H itter emerging from the pentaprisms the beams are In c nv n i nal g filf S, the k 23 directed towards each other and enter a beam-combining" m ving p r O theidfiviatfir) assflfiiated With a Scale element consisting ,of a pair of. prisms 12 and 13 with and'pointer calibrated 'directly inv termsof rangeof the a semitransparent interface; target. I Beam 1 suitors two consecutive reflections in prism 12; Thepurposeof a'r angefinder-sigh' i t0 Qbj P PQ when it strikes the interface betweenprisms Hand 13 eleVati0u' -'0f th a r 0 a fi i g t 1 1 3 required by it is partly reflected and partly transmitted. The-reflected i g h ballistics O i p f r-the rang d 'by I part is lost, the transmitted one isiutilized i a manner the rangefinder-Sig'ht. Forthis; purpose the reticle ltiis described hereafter. fitted with an aiming haircrossfzd and" the instrument eam r strikes the interfaceLafter suitering only one vis.clampedathWa'rt the barrel ofthe w.eapon..so f i ;..the

reflection m .prism i3. Again it is partlyireflected and li e'of'sight of the instrutrlentandg'fhe of -.tl1e. .weapon f partly transmitted, but this time the transmitted portionis "point t thee am? azimuth andftheyr, calafigl b w objective lens ldto 'form'two overlapping images ofj'the target onthe reticle lo-located f objective,

thusformed on the reticle 16 are viewed bythefloperator via an eyepiece'17.

lost and the reflected one is utilised.

v v thetwois varied in'i'amanner'co'rrespondingto rthe'v'aria I The useful portions ofthe beams l and .r are thuscom tions of the tangentelevation with range.

bined on the semi-transparent interface; Thatis, they To this endthemechanism; of the optical dev ator isi I henceforth follow a commonoptical pathwhich lS deSlg-f" v vniadeto drivetanother mechanism i whioh' changes the natejd l+rin FIGS. 4 and -S. tangentjelevationfangleof the sighting system;- Forzirtg stance in some 'rangefinder sights 1knownjto p'rjior1a The combined. beam l+1: 1 s,.th n collimatedin an v u required variation of the-.ta

' trumientjportrayedfinFIG 4lis rrg dly mounted i veapo'j andgthe, requiredvariation the' tang''nt t l I up frame 21 of the wedge 11% with a suitably shaped cam 26 the two deflecting elements 35r and 35l are so arranged cut to fit the ballistic curve of the Weapon. The cam acts that they produce opposite horizontal deflections of their upon alever 27 to which the reticle is attached at a point respective beams, that is, it one of the beams l and r is marked A; The reticle. can slide up or down between v deflected to the right, the other is deflected to the left. suitable guides which are'not shown on FIG. 4. The The effect of the above upon the images of the target lever is pivoted at a fulcrum F and the point of contact presented to the operator in the field of vision of the betweenthecam and the lever is marked C. A spring instrument is best illustrated by consulting FIG. 9. It 28 pulls the lever 27 upwards and thereby ensures a posiis supposed that the rangefinder-sight is rigidly clamped tive contact with cam 26 atpoint C. athwart the barrel of a firing weapon and that the latter A possible change of the range R to the target is taken is trained at a target T located at a range R The images care of by a rotation of the deviator by an angle reuired Of the tetget termed Oh the Tetieie b the beams and l to restore image coincidence; This in turn results in a a d signat d T 1 and T 1. Their spacing is0f course- ,displacement of the point C and of a displacement of determined y the range rpoint A and of the reticle. Suppose now that the barrel of the weapon, together The cam 26 is so shaped that when the instrument, with the instrument which remains rigidly clamped which .is rigidly clamped to the firing weapon, is trai d athwart it, is swung in the vertical plane running through 'so as to-align the image of the target with the haircrossthe target 50 as to change tangent eielatioh ahgie the resultant tangentelevation is that which is required of the r lby the ballistics at a new range. This condition is ful The image 1 will then drift upwards downwards filled at all operational ranges, in the field of vision but-because of the variable hori- Another embodiment of a rangefinde1'-sight known to zontal deviation produced by the element 35r-it will prior art isillustrated in H65, 6 nd 7, Th t beams not move vertically but will follow a curvilinear track of light emanating from the target are again designated shown y a soiid line On The shape of this track I and r. Upon entering the instrument they are rotated V is determined y the hOTiZOIltsi deviating Properties of by 90 degrees by suffering each a double reflection in one the eiemetlt 35% Likewise the image 1 Wiii toiiew a of a pair of pentaprisms designated lllll and Mr respectivecurvilinear tl'aek determined y the Pmhefties of the 'ly. The spacing of these prisms, B; is the base length deviating element ofthe instrument. Each beam is then collimated in an it is eieariy seen o 9 that the two tracks objective lens designated ll il and Mr whereupon the two intersect at a level marked Sihee the initial spacing beams are combined in a pair of cemented prisms 12 and between the images 1 and 1 was determined y the 13 with a semi-transparent int fa range R of the target, it follows that 1-1 is the level at The operation of these prisms is analogous to that of Which the image-Coincidence will occur for 3 target the combining prisms of theinstrurnent already discussed located at the range rwith reference to FIGS. 4- and 5. From then onward pp now that thebarrel of the weapon reverts to the two-beams follow a common path via a rectifying its original position and that the target recedes so that its roof prism 15 to form each an image of the target on a range is increased from R1 to 2 The tWO images of reticle 1 6. These two images are viewed by the operator the target are how designated 2 a 2 and the p through an eyepiece 17.. The held of visionpresented to Y ihg between them has ihel'eased because the target is the operator i hown di tic lly i FIG; 9 i i 'more distant. It is seen that if the tangent elevation of Which the images of a target located at a range R and it) the weapon is now varied, the-two images will again folf d b th bgams l d f F163 6 d 7 are d i n lowv their curvilinear tracks and will be brought into 'nated T 1 and T r respectively. coincidence at a level 2-2 corresponding to the new In order to make ranging possible an image-distorting .t zsi V rh in the optical element is inserted in the path of h f h field of vision at Which image coincidence occurs corretwo light beams between the pentaprisrns and the. objeci each to a p ifi ang R R tc. They tive. Theseelements are shown injl- IGS. 6 and 7 d can be labelled accordingly and the instrument described g are designated 351 and- 351 respectively. Each consists becomes a g h e 0f the image-distortion yp f fi i r m ifi 11 f two pairs f Each level 1 1, 22'; etc. corresponds to a specific. fcemente'd prisms chromatically eo'rnpensatedtland fsepa ta t elevation ef p The distrihutieh O I rated by a thinintervaL' In each element one prisrn' (or these levels, -3 2 Values of h t g elevatien angl imore specifically onelpair of prisms) is slightly rotated corresponding efieh g p s P the design about a p vertical axis with respect to the other, in a man and arrangementof the image-distortion elements 351' and nericleali y indicatedin FIG. .6. q 1. 351 and can be made to coincide with orjto approximate W engoing hrough the first prism (or more specifigalvery accurately the tangent elevation required by the ly the first pair (if prisms), t e m nt 35rthe1 i g ballistics of the weapon and ammunition, in which case beam; nfi'erg tw u e j i gf i ti m h the instrument described becomes a rangcfinder-sight of ftrancefgthe r "then at 'the' exit surface'so thatuponJeaVing the imageldistortion type. I

, wheni conjparedt t d lien' th ljealm a's esin turnthrough theseicond (i0 bo'res'ightedinstrument that is when the barrel of the prism:(orfmorespecifically through the seggndgpair f firing weapon remains in th e'vertic-al plane of the target.

prism fot'the. element}? "It is'obvious tromfthe. configurationof theelernentfi z th -t gi gi ef [distortion rangefinder-sight which replaces the aiming c'al defl'egtionsof the beam very nearly 'pan'oel' h 5 haircross of the instrumentsimilar to that discussed above he. h0l?iZ ontal idefie'ctions .add. -Thu the with] reference to FIGS. :4 and 5 Ingeneral, the cur- I :e mirror replicas qfithegcorrespondingtracks V ages T 1i-, -T' r .f etcq so that in general the m ngfline need not/be'strai'ght.

'Thejpurposeof thelabcnlev analysis is to] provide a broadsu scussing insomedetail at1east-on'e instrument belongmuchithesarnehappefis tqthei' e in hroiigh th'e fielement"351 'ltI SilfirlslplhC- it delle lion butisdeflected-horizontally the,elevation,ang-l'e hf the coincidence and image-distortionand to emphasize their,

-that;7;5 comm Qth horizontallyand-Vertically.' V The line M-l l on FIG. 9 is the locus of points of s'x'initial directionjQThi i coincidence of the images of the ,target for a; properly Consequently, M eNis the aimingline of the image-.

near racks ofithe'iniagesTlfTz etc in FIG. 9"

of rangefiridersights' Known to prior art byi i g toe ach o f: theInaain-categor' s-:;; 'stere0sco'pic,'jirnagca feature wln'chis that they provide one and only erenic'e to Sand .7'and are designated X r, X r, X3r. Orel s'eitcan .ybe placed along thepath of the beam one tangent elevation angle for any given range so that they can cater only to one given set of ballistics properties of the associated weapon and ammunition and therefore they become useless when the ballistics change.

Some earlier inventors have perceived this drawback andin order to obviate it--have proposed either to use a plurality of interchangeable cams or eise to mount the cam on a hinge so that its general slope could be varied; or else they have proposed a flexible cam with a variable curvature.

According to another invention made by myself, for which the application is co-pending Serial No. 475,522, now abandoned, the changing of the tangent elevation angle obtained by ranging with an image-coincidence rangefinder-sight is achieved by varying as. transfer ratio of the mechanism linking the ranging systemwith the sighting system.

These designs have several drawbacks: Interchangeable cams have the disadvantage of requiring a new cam for each set of ballistic conditions which leads to a plurality of cams. Flexible and hinged cams, known to prior art, are free of this limitation but their manufacture and calibration is expensive. Moreover, none of themethods known to prior art is applicable to the image-distortion rangefinder-sights or to the kind of steroscopic rangefinder-sights discussed with reference to FIG. 3.

The present invention is directed towards providing an improvement applicable to all rangeiinder-sights known to prior art so as to convert them into instruments which could cater to a plurality of ballistics without it being necessary to alter or complicate the mechanisms of the instrument.

The novel idea, which is at the base of the present invention, is to alter the ballistics for which the instrument caters by altering the deviating angle p of the ranging system of the increment Ap. v I

According to the present invention the required adjustable incrementa of the deviationangle p is achieved by placing an adiustable horizontally deflecting optical element such as a-wedge in the path of one of the light i eams l or r of a rangefinder sight. An element of this sort placed in front of the right-hand-side window of the rangefinder-sight and designated w is snown in FIG. SI

in fact this element need not necessarily be placed in front of the window; it can also be placed inside the.

instrument. its possible locations along the path of the luminous bearnnr of theinstruments discussed with ref- FIGS. 2, 4, -5, 6 and 7 are shown in FIGS. 23,

cations are designated X l, X 1, X l.- ,1 In eithercase the presence ofan additional horizontally deflecting, optical deviator-in one of the two beams ,of light will bodily shift the image formed by said beam towards or away from the image forrnedby the other beaniaccording to the direction in which the beam is additionally deflected; a 5 I In stereoscopic 'rangefindensig hts, such as exemplified in FIGS. 2A,. 2B and 3, this will re snltiin' an apparent appro'achiug or .r ece dingof the three-dimensional image I ofith'efield ofvision presented 'totlie operator while the' apparent distance to the markerlo-r markers asdetermined by, theispacing of the two.reticlesremains-the same Consequently the mechanism oftheinstrurnent shown'on FIGS. ZfA fand Zri -ivillfjhaveto be manipulated fin orderto match-the apparent 'jdistance tdthennarker wilh thfi 'r ij'e'w app'arent distance to'lthe target andlthe-reby the tangent elevation angle" 'ill beijch'a'nged, Likewise an increment of the tangent elevation angle to fit the tortion rangefinder-sight portrayed in FIGS. 6, 7 and 9 is best explained with reference to FIG. 10. Suppose that the additional deviator Ap is placed in the righthand-side luminous beam of the instrument and results rangefinder-sight by a suitable in a linear shift of the relevant image of the target over a distance S so that the image T r (or T r) moves to T r (T r). It is readily seen that the levels at which image coincidence occurs are now ll'-1' instead of 1-1 (or 2--2') instead of 2-2, so that the tangent elevation angle corresponding to any given range is changed and it is again possible to select the deviation Ap to fit the given change in ballistics.

The present invention has a certain imperfection which can be best explained by referring again to FIG. 10. It is seen that the locus of points of intersection of the two images of the target lies now no longer along the solid line MN but along the interrupted line M'N' which is laterally displaced by a small amount designated 1' on 'FIG. 10. This represents an azimuthal error in training the stereoscopic instrument of FIGS. 2A and 2B is free of this imperfection if the cam consists of a pair of symmetrical profiles. I

1 have found thatthe resultant azimuthal error in training the weapon is so small that itdoes not warrant the use of twoadditionaldeviators instead of one only and does not invalidate the practical value of my invention.

1. ..'Havi ng thus explained the principle of operation of the improvement according to my invention, it is fitting to dis "cuss in detail the design of one of its embodiments. it has been already stated that any conventional optical ideviator, capable of defiecting the beam horizontally by i, the relevantloa an adjustableangular amount Ap, could befit ted into a rangefinder-sight to providethe improvement according .to the present-invention and anadjustablewedgewas mentioned as onedevice which can perform this function and which is preferred becauseofits simplicity and con venience. Consequently the additional deviat on in the form of. ano'pticali wedge or a pair of Wedges will be described. In submitting the following j description. the inventor is anxious to emphasize-that he is fully aware of the factthat beam-deflecting properties; of wedge-shaped transparent'bodies whose refractive index differs from thatof J; theambient medium-are well known, so thatfoptical wedges arenot .patentable per se. What is claimed to I be novelf is theadvantage taken of the known properties ftdf'usea s imilar mechanism .to-that comprisingjitei'ns i 1 Gene n l is U i 'aip'alr o identical;counter=rotating, optical wed of wedges for. solving a: giventechnical problem; in a manner hich is new tothe art and-incorporates a er a5 'r f r pe to those designated ass-items and l9 V of inventionconsists: in-jfitting a'riy one ,of'th e ;rangefindensightddiscussed 2B, 3, 4,5;5 with an .addi-' 11' a The deviator shown in FIG. 17 may be located in the path of light at any one of the stations X X X left or right, shown in FlGS. 2B, 5 and 7. The deviator comprises a pair of identical wedges 18a and 19a placed in the path of one of the beams of light. These wedges are mounted in. circular framesfitted each with a conical gear 29a and 21a. The gears are meshed with. a third conical gear 22a disposed between the wedges, said gear 22a is driven by a hand operated knob 23a which is mounted on a shaft so as to be accessible to the operator. It will be seen that, when knob 23a is rotated, the wedges 18a and 19a are rotated through equal segments a in opposite directions.

Suppose that the angular deflection of each wedge is d and that one of them .is rotated over an angle a clockwise from the reference position in which the wedge I tapers upwards,while the other wedge is rotated over an angle a anticlockwise from the reference position in I which the wedge tapers downwards. In this case the horizontal and vertical components of the angular deviation produced by each wedge are defined by:

1st wedge- 1 horiz. component+d.sin a vert. component+d.cos a 2nd wedgc horiz. component-l-dsin a vert. componentd.cos a It is seen that the vertical deviations cancel each other, while the horizontal deviations combine additively to produce a total angular horizontal deflection Ap of the beam defined by Ap 2d.sin a The arrangement described has the merit of perforrni ing accurately the required function but is rather complex. It can be replaced by a simplified arrangement in which the second wedge is omittedaltogether. This is illustrated in PEG. l8. V l I t v In this case the first wedgewhen remaining, in the reference position in which it tapers downwardspro-" duces a vertical angular deflection d and consequentlylifts bodily the image of the target formed by the beam 1 of light which passes through the wedge. Consequently in order to makethetwovirnages level, .it becomes-necessary to'tilt accordingly the pentaprism (item ,l l'in FIGS. 2,14, 5, 6, 7) located in the path of the other beam and to immobilize it'in this position.

Again when the wedge is rotatedover an anglejva the .angularhorizontal and verticaljdeviation components of the beam of light are defined by: v i horiz. componentaisin a v yert; component-l-dcos a a It" is, readily fseenthat'the angle of rotation a can I be kept small if the deviation angle '-d'of the wedge is made-very muchlarger than the maximum required value- 'yertical,displacement changesso little that its change be ignored'and it is'legitimatetto express-the horizontal" cle- 7 if controlfknob of 'the additional'rotatable wedge :according to my invention is'fitted with a calibrated scale s le maynotnecessarily becalibratedin termsofiangw ar rotation angles a or, in terms of, theresultant angular ev-iationAp-afllt maybe calibrated inter'ins of the change" rgth e deviation; A? in orde w; akecare oft allisticsj or elseji't ean b a auses the-. ,allistics to change I I *Forins'tanc ftheirnprovement-accondingto my. in ention applied toai'rangefinder sightinorderito make of the adjustable angularzdefiection Ap: in which case the ndlpointer to" ascertain; the amount of rotation of the edge rrorn the reference position; For convenience the t. th t' ngentgelevatipnfangle fe obtained by ap l 5 d li i i nl l deviattr q i t ch e alibrated'j in term of the come all functions of the propellant temperature. In

this case the graduations of the scale of the control mechanism of the additional deviator according to my invention might be arranged and labelled in terms of propellant V temperature variations, which cause the ballistics to change.

Another embodiment of the present invention is applicable to rangefinder-sights known to prior art whichbecause of thermal or mechanical instability of their ranging systemsare fitted with an adjusting device variously designated in the trade as zero setting or infinity alignment or field alignment device.

it is evident with reference to FEGS. 2A, 2B or 6 and 7, that the operation of the ranging system of the instrument will be upset if its body bends slightly in the horizontal plane. Such bending may be caused by mechanical strain or may occur as a result of changes in ambient temperature. The operation of the rangefinder-sight will also be upset if the position of one of the vital elements of its optical system slightly changes with respect to the other elements during the lifetime of the instrument.

The conventional procedure to check whether a rangefinder or rangefinder-sight remains in proper alignment is to train it on a target located at aknown range or else at an object, such as a-lath, which simulates a target located at a known range, and to check whether the images of the target are*presented' to'the operator in proper relationship for-the known range of the actual or simulated target.

The lack of proper relationship indicates the presence rected'or minimised atrother rangesby bringing the images into proper relationship by a separate adjustable fhorizontal deviator called zero adjustment of infinity alignment or held alignment.

trary fixed scale 5-1 of the knowninfinity adjustment deviator is illustrated in FIGS.,11 and 12; for the case where jthe instrument was found to operate properly (FIG. 11) and whereit, was found necessaryto correct an instrumental error by setting the deviator. in a position corresponding tor -a reading of two graduations' on the arbitrary fixed scale:(FIG. 12) respectively. t It follows that thisv deviator, known to prior art, performs the same basic physical function as the deviator according to my. invention whichis to deviate angularly,

in thehorizontal, plane, one of thebeams of the instrurnent byan adjustable amount. Yet'the purpose of this function is solely to maintain the stability Of the operation 1. of the ranging system of the'instrument and isktherefore,

.not related "in anyway to; the function of the deviator accordin'g'to my invention, whose purpose is to make the 'rangefinder-sight suitable for a plurality of ballistics of "the associated firing weapon; v i 'f'Th'e difference between the purp Qstable' rangefinder-sight can: be corrected B a zero a ya jt bu i The rotating control knob 5t) withvpointer and an arbia I sesof the two devia tors becomes still clearer. if i it isicon'sidered that an ong 11 san 13 a zero adjustment deviator'to correct possible subsequently developing'faults of the ranging system, must still be fitted with a deviator according to my invention in order to cater for a plurality of ballistics.

The above line of thought leads to an alternative embodiment of my invention, which consists in modifying in a'no-vel 'manner the driving mechanism of the zero adjustment deviators known to prior art so as to convert them'into dual function devices which would both correct possible faults in the ranging system of the rangefindersight*whichfunction is known to prior art, and would also'perform the novel function; of compensating for changes of ballistics of the associated weapon.

The conventional deviator discussed with reference to FIGS; 11 and 12 is now converted into a dual-purpose deviator by supplementing its control mechanism inthe manner shown in FIGS. 13, 14 and 15. The new element is a disk 52 on'which a scale 53 calibrated in terms of the known factorwhich causes the changes in the ballistic curve is engraved-,[while the arbitrary scale of the infinity adjustment proper remains unchanged. To be specific it will be supposed that the rangefinder-sight was designedorig'inally for a ballistic curve prevailing when the temperature of the repellant is 70 F, that the muzzle velocity and theballastic vary with propellant temperature and that the instrument has to cater for ballistics prevailing at temperatures ranging from 30 F. to 90 F. It is supposed that'the required increments-hp of the deviation angle p were computed according to the present invention and the corresponding settings of the adjustable de'viator are marked on the scale or the disk as shown in FIGS-'13, 14-and '15 on which the temperature mark of 70 F. is supplemented with a letter R (for Reference temp).

In the arrangement described, the disk 52, with the temperature scale 53 can either remain fixed by locking it to the bodyof .the instrument while the control knob Silo of the deviator'is rotated or 'else'it can be locked to the knob and rotate with it. t

The associated deviator is not shown but may be of any conventional type including the single rotatable wedge type "or the pair oflcounter-rotating wedges type similar to those showninFlGS. l8 and 17 respectively, but inftendedispecifically-for use as an infinity adjustment device for correcting errors of the ranging system of the instrum'ent. I

-For'init'ial factory alignment the setting isas shown in FIG. 13 and the disk 52 is fixed tothe body of the instru:

. ment; the instrument leaves the factory in this condition; I When the rangefinder-sight is used, the knob Etta i's-set to;

readuon the scale"53 the temperature prevailing at the time of use. A i

lice. target or lath as orv jmage coincidence,

f thera'ngefindinggsystem Brine 'Supposetltat 1r or subsequent rechecking the instrumentpthe knob,

' 56a is broughtbackto 'read 'the referencetemperature of as shown'inFiG. 13" irrespective ofrthe-actua lly" prevailihg. temperatureQ-V A lock i(no't shown) fixingth i,

' disk 52 the body or theinstrument is thenreleasedand I' the"disk is locked to the knob, whereupon the alignment :routine is carried out'bytraining the'instrument on a referv 0 possible-"Chang described above and by. checking former occurs 1- trument is ltd corrected by rotating Q g t t in Whichrt -h is the air density l lfiring weapon. For instance the position of the control knob for a temperature of 57 F. is shown in FIG. 15.

In this description the actual mechanism operating the infinity adjusting optical deviator, the shape of the scales and the way of locking and unlocking the disk are immaterial. In fact any known method may be used. The essential fact is the use of the adjustable optical deviator for a dual purpose, one of which: the infinity setting is known to prior art, the other; the catering for a multiplicity of ballistics, is novel.

The method is perfectly accurate only if the relationship between the angular deviation increment hp and the displacement of the infinity adjustment control is linear. If it is not, the method is approximate only; I have found, however, that in practice the error is small enough to be neglected.

The principle of operation of the improvement according to the present invention and its preferred embodiments have been described. it remains to prove whether and to what extent the invention performs the function of catering for possible variations of the ballistics of the associated weapon. It is also the duty of the inventor to teach that magnitude of the additional angular deflection Ap which should be selected to achieve optimum results in any given circumstances. To do this it is necessary to go into the theory of external ballistics of a firing Weapon.

The mathematical formula expressing the magnitude of the tangent elevation angle E required to score a hit on a target located at a range R is the ballistic equation of the Weapon and a graph representing said ballistic equation in Cartesian coordinates is the ballistic curve.

It is well known that the following formula is a close approximation of the ballistic equation:

in the above formula:

g is the gravity ,acceleration y is the muzzle velocity jis the angle of jump of the weapon i is the retardation coefiicient of the projectile The retardation' coefiicient r is defined by the formulaz' c is; theform factor of the projectile m is the "mass of the projectile A is'thevcross sectionl area ofthe projectile a possible change or the "muzzle velocity 1 or else a L the retardatio :"Ihe" relation be rammed e result [Equation .4 is accurate enough for'practical' purposes "if the muzzle velocity-is -lower than thespeed'ofsound I and if the target'is approximately at; the same level 'asthe' It-is seen frorn Eqnationt that thetwo factors which might --al'r"ect the magnitude of the tangent'elevation angle E required-to sco'rega hit on a targetat arangeER are? {charge is chang dfiotQ-if its rate .of burnirig fvaries'; the l, v

atteroccurs'iftheprojectile is changedgf,

ents ncfrement On the other hand the change of the parallax angle p by an increment Ap according to the present invention results in an increment AE of the tangent elevation angle E defined by v R) 2 A? (6) The first and second partial dififerentials can be determined from Equations 4 and 1 respectively: The result becomes:

5E 1 t. (a 2@ 3 (E 2 Ei p 1 Q By substituting these expressions in Equation 6 we get: li. AE U2 gqB 14- 2112 Ap It is seen that the increment 5E which can be obtained according to my invention is not identical with the actual increment AE of the ballistic curve as defined by Equation 5, which means that my invention does not make it possible to compensate for any possible changes in the ballistic curve at all ranges and that a residual error e is left. This error is defined by the equation: I

' mu l- By combining Equations 5, 7 and 8 we get:

It is now seen that the residual error e vanishes fortwo values of R: one is 12:0, the other R=R is a range at which the term-insquare brackets vanishes.

This is illustrated in 1 FIG. '16 which is a graph in' Cartesian coordinates showing a plot of three ballistic curves versus range. Only the portionof the graph corre-.

sponding to'positive values or R has a physical significance.

: The first designated IE is the ballistic curve of the weapon for which the rangefinder-sight was originally designed;

n oi"theweapon. V i n {The-thirdcurve--designatedEl-AE is one oi the plural-1 vity of tangent elevation.;ver'sus range curves which the. rangefinder-sight can provide, if fitted with the improve ment according to the present "invention. The residual ofjthe tangent elevation angle are represented by' 1 e rors: 7

' dinates oftheshaded areain the graph. I obyious that the range R6, at which intersect and the; residual error .e jthe choice of the' devia'tion angle- An spending deviatioiiian'gle A'p can' -be determine tion 9 andis grven'gby theexpressio the curves E I conv ersely'-,t he? value, of the rang? can' be selected arbitrarily;.jin:,whic h case the corret ma n 1% from Formula 9. The minimum and maximum operational ranges are'designated in FIG. 16 by the symbols R and R respectively and for the sake of clearness of representation, the graph is drawn not to scale so as to exaggerate the magnitude of the residual error.

What I claim is:

l. in a rangefinder-sight of the type which is clamped 'athwart the barrel of a firing weapon in which the parallax angle subtended by two beam-s of light emanating from the target and entering each one of a'pair of spaced windows is determined by bringing into proper relationship the two images of the target presented to an operator and formed each by one of said two beams of light, and the tangent elevation angle of the barrel as required by the ballistic curve of the weapon of any operational range corresponding to said parallax angle is automatically obtained by bringing the two images of the target into proper relationship, said rangefindcr-sight including a first optical deviator mounted in the path of one of two beams of light, and means for actuating said first optical deviator to adjust said beam of light for ranging as required by a prescribed ballistic curve of the weapon; and a second optical deviatoroperably mounted to selectively and continuously adjust the beam of light from said first deviator so as to further deflect the said adjustable.

beam of light in the plane of the base of the rangefindersight by any adjustable angle for deliberately changing the saidparallax angle and for producing a corresponding change in the setting of the instrument whereby the two images of the target are brought into proper relationship corresponding to any change in the tangent elevation angle of the barrel as a result of a change in the ballistic curve of the associated weapon.

2. A rangefinder-sight as set forth in claim 1 in which said second deviator comprises a wedge rotatably mounted in the said adjustable beam of light and means operable for rotating said wedge to further deflect said beam oi -light whereby the parallax angle of the first deviator is changed to meet said new ballistic curve so 7 that further operationlof'the said first deviator deflects the zuijustable lightbeam as required by the new ballistics of the weapon without the requirement of mechanical adl 'justment of the parallaxangle of saidfirst deviator" said adjustablemeans-tori said second. deviator is ';-pr,o- .j -=;vided' witha s'caleand pointer, saidgiscalegbeing calibrated actorsfwhich cause the ballistic curve to I eleyationangles as defined this modifiedballistic curve in terms of thef 3. A rangefinder-sight as set forth in claimZ in which i saidadjustable means for said second deviator is provided withla scale and pointer, said'scale .being calibrated in terms of the factors which cause the ballistic curve to' vary.

4. A raugefinder-sight as set forth in claim 1 in which said second deviator comprises a pairof counter-rotating wedges rotatably mounted in the said adjustable beam of light and means operable for rotating said pair of coun-- v ter-rotatingwedges to furtherdefiect said beam of light whereby the, parallax angle of thefirst deviator is changedtomeet-said new ballistic'curve so'that' further operation of thfi said; first deviator deflects theadjust'able -lightbeam as re quire'dlby the ballisticsoffthe weapon withou-t thefr e quirement of mechanical adjustment of the [parallax angle of said first deviaton-P 7 ,1 l 5;. A ra'nge'finder-sightias set .forthin claim 41in hich" 

1. IN A RANGEFINDER-SIGHT OF THE TYPE WHICH IS CLAMPED ATHWART THE BARREL OF A FIRING WEAPON IN WHICH THE PARALLAX ANGLE SUBTENDED BY TWO BEAMS OF LIGHT EMANATING FROM THE TARGET AND ENTERING EACH ONE OF A PAIR OF SPACED WINDOWS IS DETERMINED BY BRINGING INTO PROPER RELATIONSHIP THE TWO IMAGES OF THE TARGET PRESENTED TO AN OPERATOR AND FORMED EACH BY ONE OF SAID TWO BEAMS OF LIGHT, AND THE TANGENT ELEVATION ANGLE OF THE BARREL AS REQUIRED BY THE BALLISTIC CURVE OF THE WEAPON OF ANY OPERATIONAL RANGE CORRESPONDING TO SAID PARALLAX ANGLE IS AUTOMATICALLY OBTAINED BY BRINGING THE TWO IMAGES OF THE TARGET INTO PROPER RELATIONSHIP, SAID RANGEFINDER-SIGHT INCLUDING A FIRST OPTICAL DEVIATOR MOUNTED IN THE PATH OF ONE OF TWO BEAMS OF LIGHT, AND MEANS FOR ACTUATING SAID FIRST OPTICAL DEVIATOR TO ADJUST SAID BEAM OF LIGHT FOR RANGING AS REQUIRED BY A PRESCRIBED BALLISTIC CURVE OF THE WEAPON; AND A SECOND OPTICAL DEVIATOR OPERABLY MOUNTED TO SELECTIVELY AND CONTINUOUSLY ADJUST THE BEAM OF LIGHT FROM SAID FIRST DEVIATOR SO AS TO FURTHER DEFLECT THE SAID ADJUSTABLE BEAM OF LIGHT IN THE PLANE OF THE BASE OF THE RANGEFINDERSIGHT BY ANY ADJUSTABLE ANGLE FOR DELIBERATELY CHANGING THE SAID PARALLAX ANGLE AND FOR PRODUCING A CORRESPONDING CHANGE IN THE SETTING OF THE INSTRUMENT WHEREBY THE TWO IMAGES OF THE TARGET ARE BROUGHT INTO PROPER RELATIONSHIP CORRESPONDING TO ANY CHANGE IN THE TANGENT ELEVATION ANGLE OF THE BARREL AS A RESULT OF A CHANGE IN THE BALLISTIC CURVE OF THE ASSOCIATED WEAPON. 